Emissions from industrial processes often require treatment by pollution control systems. Generally, the industrial process emissions are drawn from the process equipment by a low pressure fan, ducted to the pollution control equipment and, after treatment, drawn from the pollution control equipment by a high pressure fan. The nature of most pollution control equipment requires that a plurality of valves be employed which are constantly cycling between the open and closed condition. Such cycling induces pressure and flow variations in the industrial process exhaust system.
The problem to which the present invention presents a solution is that certain industrial processes are sensitive to pressure fluctuations in the exhaust system therefrom. When the exhaust is connected to a pollution control system the problem is exacerbated. For example, in a conventional pollution control system, a high pressure exhaust fan exerts a suction of, for example, 20 to 40 inches water column on the discharge end of, for example, a thermal oxidizer. As many as 24 valve changes from open to close or close to open may occur in a 90 second period. Pressure fluctuations across the pollution control equipment are transmitted back through the industrial process exhaust ductwork thereby causing a similar fluctuation at the outlet of the process equipment which may seriously compromise industrial process efficiency.
Accordingly, there is a need for a pressure regulator that senses fluctuations in pollution control equipment and offsets the fluctuations by a compensating change in upstream duct pressure. The regulator preferably minimizes pressure fluctuations in the industrial process exhaust ductwork without requiring the introduction of additional air which compromises pollution control efficiency. Mathematically, the sum of pollution control equipment pressure and regulator pressure should be a constant at a given flow rate whereby pressure fluctuations in the pollution control system are not transmitted back to the industrial process equipment.